Activated sludge and clarifiers: wastewater treatment plants in Pennsylvania
234 plants · 30% of the state · 449 MGD reported by 225 plants
Klarifi identifies 234 publicly owned wastewater treatment plants with activated sludge and clarifiers in Pennsylvania, 30% of the 790 plants in the state (449 MGD reported by 225 plants). The largest is City Of Erie, Pa - Wastewater Treatment Plant in Erie at 44.59 MGD.
Activated sludge is the standard mechanical process for cities: aeration basins where bacteria consume organic matter, followed by clarifiers that settle the biomass out. These plants are identified by their circular or rectangular clarifiers and by the suspended-growth process code, and they are the main market for blowers, diffusers, clarifier mechanisms and instrumentation.
The largest activated sludge plants in Pennsylvania
| # | Facility | City | Avg flow (MGD) | NPDES permit | Expires | Violations (3y) |
|---|---|---|---|---|---|---|
| 1 | City Of Erie, Pa - Wastewater Treatment Plant | Erie | 44.59 | PAL026301 | Dec 2030 | 1 |
| 2 | City Of Allentown Wastewater Treatment Plant | Allentown | 31.66 | PA0026000 | Sep 2007 | 0 |
| 3 | Delcora-Western Regional Treatment Plant | Chester | 30.48 | PA0027103 | Mar 2026 | 18 |
| 4 | Reading STP | Reading | 14.02 | PA0026549 | Apr 2028 | 9 |
| 5 | City Of Bethlehem Wastewater Treatment Plant | Bethlehem | 10.23 | PA0026042 | May 2031 | 18 |
| 6 | Springettsbury Wastewater Treatment Plant | York | 9.09 | PAL026808 | Dec 2030 | 4 |
| 7 | Gr Hazleton Jt Sew Auth WWTP | Hazleton | 6.71 | PA0026921 | Feb 2027 | 6 |
| 8 | Oaks WWTP (lower Perkiomen Valley) | Oaks | 6.7 | PA0026964 | Nov 2030 | 5 |
| 9 | Washington E Washington STP | Washington | 6.15 | PA0026212 | Jan 2031 | 169 |
| 10 | Uniontown STP | Uniontown | 6.09 | PA0027219 | Jul 2027 | 6 |
Contacts and project signals for every plant on this list
Klarifi adds verified decision-maker contacts, permit limits, discharge monitoring data and the capital projects planned in each city, filterable by technology, size and compliance record.
Other technologies in Pennsylvania
Activated sludge and clarifiers in other states
Activated sludge and clarifiers in Pennsylvania: questions
Sources and methodology
Flow, permit and violation figures come from the EPA's ICIS-NPDES discharge monitoring records. Population served comes from the Clean Watersheds Needs Survey 2022. Treatment structures are identified by Klarifi's review of aerial imagery, and capital improvement projects are extracted from published municipal budget documents. Violations are counted over the last three years of monitoring reports.
Data refreshed October 26, 2026.
Wastewater terms: Activated sludge · Biological nutrient removal · Equalization tank · NPDES permit · POTW · all terms